Dirt and other contaminates, such as grease, pollen, hair spray, etc., on air-conditioning coils present a serious maintenance problem in residential or commercial buildings. Dirty coils reduce airflow, decrease efficiency, reduce HVAC capacity, and are a major cause of compressor failure and sick building syndrome.
Indoor coils known as evaporator coils are located in the air handler portion of the system and are generally fitted with intake filters. Filtering is important because indoor coils are located in tight spaces within the air handler ductwork and so they are difficult and expensive to clean. Therefore, a filter is the first line of defense against contaminate intrusion into the system. However, such filters are often not efficient or the framing around the filter is improperly fitted, thereby allowing contaminates in the air to circumvent the filter. In addition such filters are often neglected and become ineffective.
Indoor coils located within the air handling system are also fitted with drain pans to collect and dissipate moisture buildup from the coil. These pans also require careful cleaning to prevent their accumulated debris from producing molds that may becoming airborne and polluting the air passing through the coil.
The most efficient and most expensive and time-consuming way to clean an evaporator coil is to pump down the Freon and disconnect the lines from the coil, tape over all the open ends of the lines, take the front cover off the coil and slip it forward out of the case, then clean with steam or high pressure using a solvent prescribed for such coils. Then one must reverse the order of removal and reconnect the refrigerant lines. A vacuum must be imposed on the lines for at least an hour before releasing Freon back into the system. Only a person certified to work with Freon must do this process. Further care must be taken to contain the mess created by coil removal and cleaning, but containment and careful cleanup is important to protect indoor air quality.
Other methods for cleaning evaporator coils may be used. Provided sufficient space is available, a bottle brush may be used to clean the coil to some degree. However, loosening such debris simply allows the contaminates to become airborne or settle in the drain pan which may contain water, thereby requiring additional effort to clean. Coils positioned in an up-flow furnace system require a covering over the furnace heat exchangers to keep debris from falling down into the furnace. Often a bottlebrush and a squeeze bottle of water is used in this process to keep the contaminates on the coil damp, thus missed contaminants become even more adhered to the coil and thus harder to remove. In some cases alkaline cleaners are effective at cutting greasy dirt encountered on indoor coils. Grease comes from skin flakes and cooking. Using powerful foaming cleaners requires experience and extreme caution, especially indoors where fumes could sicken the technician or building occupants. The use of such foam cleaners also results in a sticky residue on the coil and, if not removed with a water bath and brush, will actually attract contaminates and make them harder to remove at the next cleaning.
Since the evaporator coils are covered with very fine, very sharp fins that serve as heat exchangers, care must be taken to insure that these fins do not become damaged. High pressure water or vigorous brushing may damage the fins and thus reduce the effectiveness of the coils' ability to exchange heat. In the tight, very confined space within the air handling system it is very hard to prevent such damage with water bottles, spray cans and conventional brushes.
The most common type of AC coil is the A-frame type whereby a pair of coils is arranged back-to-back forming an “A”. Such coils are placed in the air handling system so as to pass intake air across the coils, using a blower fan, and into the ventilation ducts. Contaminates in the air stream tend to settle on the face of one coil and on the under side of the adjacent coil. Using brushes, foams, water spray and the like to clean the exterior faces of coils while in place simply forces the contaminates further into the coils because of inaccessibility of the coils from either side.
Conventional vacuum systems have been used to assist the bottlebrush process, but, again, the brush loosens contaminates that either fall into the drain pan or remain airborne. A conventional vacuum system head, in some cases, may be used that has a non-active brush or a rotary brush that has very short bristles, commonly used for cleaning furniture, neither of which are particularly efficient in vacuuming coil fins in such narrow confines, nor do they have the size or reach to extend through the coil fins from either side. Bristle type and size is essential to effective cleaning of any coil having fins and especially so in evaporator coils. Bristles for this purpose should be sufficiently tough to resist being cut by the sharp fins, yet be fine enough to slide easily between the fins and still be sufficiently rigid to remove the contaminates. A vacuum brush should also be driven so as to loosen and remove by vacuum, and possibly vibration, all contaminates within the confines of the coil's air handling compartment while effectively containing airborne elements.